1. Field of the Invention
The present invention relates to a beacon scheduling system and method for preventing beacon overlapping, and more particularly, to a beacon scheduling system and method in which a router existing in a ZigBee network transmits beacons in consideration of a beacon interval by scanning the beacons.
This work was supported by the IT R&D program of MIC/IITA [2005-S-038-02, Development of UHF RF-ID and Ubiquitous Networking Technology]
2. Description of the Related Art
According to a suggested beacon scheduling method in a conventional ZigBee network beacon mode, information on a time slot for transmitting beacons is identified using beacon arrival times of neighbor nodes obtained by scanning information of the neighbor nodes and an offset of a parent beacon of an adjacent node included in a beacon payload.
According to this method, the beacon transmission time slot of a specific router is determined based on the beacon reception time. Therefore, the beacon reception time for each router should be stored to be used to calculate the time slot for each router.
However, a significant problem arising with this method lies in that, if there are routers starting simultaneously scanning beacons, the routers may select the same beacon transmission time slot (hereinafter, beacon slot) almost at the same time, thereby colliding against each other.
To prevent such overlapping, a centralized management method in which a management server or a sink node controls routers to select different beacon slots can be used. However, this method may cause an overload to the management subject and traffic congestion in an initialization process.
In addition, another problem is that the number of beacon slots to be allocated is limited so that the beacon slot of a specific router can be reused out of a radio wave reaching distance of the router. Furthermore, it is not easy to prevent beacon overlapping within the radio wave reaching distance.